1. Field of the Invention
The present invention relates to an improved rail gun launcher having much greater efficiency and durability in comparison to conventional rail gun launchers. More particularly, to such a rail gun launcher with a unique multi-turn armature structure which can be continuously accelerated to a hypervelocity (a velocity approximately 3,000 meters per second or greater) in a very efficient manner involving much less power consumption and a comparatively smaller power source than has been previously possible, and wherein the overall structure of the rail gun launcher is relatively uncomplicated.
2. Description of the Background Art
Known electromagnetic accelerators have been designed to accelerate and launch projectiles at high velocities. An example of such an electromagnetic accelerator is a conventional rail gun comprising parallel conductive rails (which are fixed in position) and a conductive armature (or projectile) which is accelerated to great speeds sliding or rolling along the conductive rails when a very large power source such as a million amps is connected across the rails. The rails and the armature together form a closed single turn electrical circuit. When the parallel conductive rails are connected to the large power source, the conductive rails allow a large electric current to pass through the armature. Electric current runs from one terminal of the power source, up one conductive rail, across the armature and down the other conductive rail to the other terminal of the power source. This flow of the current creates a powerful magnetic field between the conductive rails and the projectile. This magnetic field in connection with the current across the armature creates a Lorentz (or propulsion) force which substantially continuously accelerates the projectile along the rails away from the power source until the armature reaches very high speed and is launched.
An example of such a conventional rail gun is found in U.S. Pat. No. 4,928,572 to Scott issued on May 29, 1990, which discloses an electromagnetic projectile launcher using a pulsed AC generator with a power source. The generator is operative to supply a relatively low current pulse to initially accelerate the armature after which an extremely high current pulse is applied for main acceleration. The pre-acceleration pulse may be derived from an auxiliary winding on the generator or may be provided by a relatively smaller generator operated in synchronism with the main generator or physically coupled thereto.
Another example of such a conventional rail gun is found in U.S. Pat. No. 5,297,468 to Dreizin issued on May 29, 1994, which discloses a railgun apparatus for accelerating a projectile having a conductive region. The railgun comprises a power source for providing a current impulse and at least two elongate generally parallel rails. The rails include a first layer comprising a highly conductive material and a second layer comprising a highly resistive layer. The second layer has a resistivity that varies along the length of the rails and is so sized and arranged as to contact the conductive region of the projectile. The power source is switchably connected to the first layer of the rails. When the current impulse is applied to the rails with the projectile therebetween, the current impulse is spread over the conductive region of the projectile to reduce the velocity skin effect.
While conventional rail guns are in principle very simple, they have several known disadvantages, making them practically difficult. One known disadvantage is that, since the conventional rail gun involves only a single turn construction with the rails and armature, an extremely high current DC power source is required. Rail guns require the current flowing through the rails and the projectile to be in the magnitude of tens of thousands to millions of amperes in order to generate the high velocity of the projectile which is sought. A related disadvantage is that the extremely high current is required to be generated over a very short period of time. Without such a high current generated over such a short period of time, the armature would fail to be launched at an appropriate velocity. A power source which can generate such a high amount of current over such a short period of time is both large in size and expensive.
Another disadvantage is that since the armature must be in constant physical contact and electrical conductivity with the rails to let electric current flow as the armature is being launched, large amounts of heat are generated between the moving armature and the rails which burns the rails thereby causing significant and rapid wear of the rails. Although the rails are firmly anchored, under the application of very high current such as one million amps the rails will move a very little amount. That very little movement creates a little gap in the contact between the armature and the rails, and the little gap causes arcing which creates the tremendous heat that destroys the rails. Thus, conventional rail guns can only be used for a single operation or a small number of applications due to the damage to the rails caused by launching of the armature. One manner of avoiding burning of the rails via friction heat is use of plasma arcing, but plasma arcing generates even greater heat so that it is not an effective solution to the problem.
Another disadvantage of conventional rail guns is that, because the armature and two rails are connected in a series-type connection electrically, the heat loss on the rails increases while the armatures, which is only a small fraction of the length of the rails, moves along the rails from breech to muzzle. The point at which the power source (which is usually a DC power source) is connected to the rails in the conventional rail guns must be the breech end close to the initial position of the armature. Thus, as the armature moves away from the breech end, the efficiency of the rail gun will decrease as the effective length of the rails, i.e., the distance between the power source and the armature, increases. As a result of this, the efficiency of typical conventional rail guns such as those of Scott and Dreizen is only approximately 10-30%.
In order to reduce the heat loss along the rails, a more advanced type of rail gun uses segmented rails. As with the conventional rail guns described above, a rail gun which uses segmented rails is composed of parallel arranged current-conducting rails which are connected with a high-intensity current source which accelerates the projectile along the length of the rails. However, unlike a conventional rail gun, a segmented rail gun uses many pairs of shorter length rails lined up front to back, with each pair of shorter length rails being connected to a separate power source. Thus, since each pair of rails is connected to a separate power source, the need for a relatively high power source is somewhat alleviated and the efficiency of a typical segmented rail gun is increased from that of a typical conventional rail gun to approximately 40-60%. However, since the segmented rails are arranged front to back and the segmented rails need to have commutation between the rails in order for the projectile to be accelerated long the entire length of the rail gun, segmented rails guns are known to have a problem with electricity arcing between the pairs of rails. Also, complexity of the segmented rail guns is significantly increased because the multiple power sources must be properly connected to the rails and properly switched over time. Examples of such segmented rails guns can be found in U.S. Pat. Nos. 4,343,223 to Hawke et al. issued on Aug. 10, 1982, 4,754,687 to Kemeny issued on Jul. 5, 1988 and 5,431,083 to Vassioukevitch issued on Jul. 11, 1995.
In an effort to improve the efficiency of conventional rail guns, another type of rail gun, called an augmented rail gun, uses multiple parallel rails to increase the magnetic field strength in order to improve the propulsion force acting on the armature. Such an augmented rail gun can be seen in U.S. Pat. No. 5,375,504 to Pauer issued on Dec. 27, 1994. However, with such augmented rail guns, while the propulsion force is increased, the efficiency is decreased/scarified because the total length of the rails is multiplied, and (again) complexity is increased.
A second example of an electromagnetic accelerator is an induction coil launcher, such as a ring launchers or an eddy-current launcher. Induction coil launchers create an induced current on the armature/projectile which repels the source current within the body of the induction coil launcher. The induced current on the projectile causes the projectile to move towards the lesser reaction thereby pushing the projectile forward. Electrical control circuits are used to control the coils on and off, so that the coil(s) adjacent to the projectile is always on while the projectile is moving forward. Such induction coil launchers are disclosed in U.S. Pat. Nos. 5,125,321 to Cowan Jr. et al. issued on Jun. 30, 1992 and 7,111,619 to Schneider issued on Sep. 26, 2006. In both such induction coil launchers, sensors and switches are used to control the coils on and off. While the induction coil launcher initially quickly accelerates the projectile, induction coil launchers have known disadvantages.
For example, due to the high velocity of the projectile which is being accelerated, the switches turning on and off the coils must work at an extremely high speed. Further, each coil inherently has a certain substantial amount of inductance which will prevent precision switching between on and off of the power to the coils. As such, a precision control circuit to turn on and off each coil depending on the position of the projectile must be added to the induction coil launcher. However, such control circuitry for high-speed precision switching with high current has high technical difficulties in any practical application. This becomes especially true when turning off a coil of a section of coils with high current energy stored therein due to inductance. The turning off operation can cause very large arcing by the mechanical switch which causes the contactors to burn, or if extra time is taken to bleed the stored inductance energy, this slows the switching speed. Further, by using switches, an inductive loss usually occurs. Thus, every time a switch turns off the current flow, the stored inductive energy must be converted to heat in order to be dissipated.
Another example of an electromagnetic launcher is a helical coilgun. A helical coilgun consists of an armature coil and a stator coil in coaxial configuration. Such helical coilguns are shown in W. R. Snow et al. “Design Criteria for Brush Commutation in High Speed Traveling Wave Coilguns”, IEEE Transaction On Magnetics, vol. 27, No. 1, January 1991, pp 654-658 and U.S. Pat. No. 7,077,047 to Frasca issued on Jul. 18, 2006. In a helical coilgun, rails are used with a sliding contact to supply power and commutators which connect between the armature coil and the stator coil. Current is caused to flow within the armature coil in the opposite direction of current which flows in the stator coil, thus causing the armature coil to be repelled from the stator coil. While the projectile is moving forward, the stator coil or a portion of the stator coil is connected to the projectile and therefore moves forward with the projectile.
A known disadvantage of the helical coilgun is that when the stator coil or section of the stator coil is disconnected from the projectile, there is a large energy discharge. Because of the inductive nature of the coils (as discussed above), the discharged energy creates arcing that wears and burns the commutators and contacts. Further, commutators themselves also have an inductive loss and, just as with the coil launcher, when a current carrying section of the coil turns off, the stored inductive energy must be converted to heat in order to be dissipated.
The present applicant has previously proposed a channel gun electromagnetic launcher as an improvement over the conventionally available electromagnetic launchers, see U.S. Pat. No. 7,614,393. In such channel gun magnetic launcher, conductive rails are disposed in spaced, substantially parallel relation to each other with a plurality of conductive rungs interconnecting the rails, and normally-open switches are associated with the rungs for selectively permitting current flow through different ones of the rungs as an armature/projectile is accelerated along the rails. The non-conductive, magnetic armature moves parallel to the rails without coming into electrical contact with the rails or the rungs of the guide. Current is allowed to flow through the rungs when in the vicinity of the projectile and then being turned off when the projectile is no longer adjacent to the rungs, thereby creating a magnetic field which propels the armature (and any associated projectile) along the guide.
While such previously proposed channel gun magnetic launcher represents a significant improvement over the conventionally known launchers, since the launcher still requires the use of precision switching and associated circuitry, there are practical difficulties in which must be addressed when accelerating a projectile to hypervelocities sufficient to launch the projectile into space, especially for large-scale applications.
Although some of the disadvantages of conventional electromagnetic launching systems have been addressed, as discussed above, a need still exists in the art for an improved, more efficient electromagnetic launching system which more completely addresses all of the disadvantages attendant the conventional systems. In particular, there is a need for such an improved system that may continuously and efficiently accelerate a projectile but which does not involve control circuitry including commutation or switching circuits so as to reduce inductive loss, which reduces rail wear for repeatable use so as to ensure a long working life and permits the use of a comparatively smaller power source.